using clojure.java.jdbc, is there a way to execute a sql statement not in a block?

=> (clojure.java.jdbc/execute! -db "DISCARD ALL")
PSQLException ERROR: DISCARD ALL cannot run inside a transaction block  org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse (QueryExecutorImpl.java:2422)

@wei Use db-do-commands instead of execute! -- then you can tell it to not use a transaction.

(clojure.java.jdbc/db-do-commands -db false "DISCARD ALL")

(also, if it helps, there's a #sql channel for in-depth JDBC / SQL questions)

@seancorfield perfect-- thanks!

ok I'll ask on #sql for future questions

In general, the assumption is that DDL should be run with db-do-commands and SQL run with query / execute! (and the various insert and delete functions)

I see. for context, this is a workaround to a problem I discovered after upgrading postgres. the most recent version caches prepared statements, so sometimes a migration that changes a table will trigger an error when a cached query is run against that table

PostgreSQL is a strange beast.

is here a replacement to gloss?

or just use gloss even though it’s been archived.

clojure.spec is very useful for taking apart structured data. What is the most similar option for strings? I'd like to put a string into a parser and get a labeled tree out of it.

@dottedmag, maybe Instaparse is what you want? https://github.com/Engelberg/instaparse

@jduhamel, we do use gloss in production even though it's been archived and it works fine for us (although it could maybe have more batteries included and nicer exceptions and...). I'm not aware of a replacement.

@miika Thanks. I was not thrilled by a string-based parser declaration when I looked at it. I'll give it a second try.

Oh, it does have PEG, so I can write ordered choices. Sweet.

Search the README for instaparse.combinators - you can declare the parsers with Clojure data as well

Yep, read up to it already. This README is long, and I didn't expect it to have two interfaces 😃

How can I insert record into this table with clojure.java.jdbc and postgresql?

CREATE TABLE accounts (
  id serial primary key
);

;; This function call throws PSQLException. It generates invalid query for postgresql.
(clojure.java.jdbc/insert! db :accounts {})
;; This works, but cannot get generated ID as return value
(clojure.java.jdbc/execute! db ["INSERT INTO accounts (id) VALUES (DEFAULTS);"])

general question about lib deployments to clojars. Is there a best practice for the naming of artifacts? I've seen quite a number of projects deployed without an artifact name prefix, and when there is a prefix, is it considered narcissistic to use your own handle vs some generic grouping or possibly the artifact name itself (`[somename/somename "1.0.0"]`)?. How about the clj- pattern for the project name part of the artifact id? For reference and as two examples of well known clojure libs with both patterns in them, [clj-http "3.8.0"] has no prefix and uses the clj- pattern, whereas [com.rpl/specter "1.1.0"] has a prefix and no clj- pattern.

Hi all, why doesn't this work (map #(% 2 3) '(+ / * -)) but this does? (map #(% 2 3) (list + / * -)) In particular, I'm confused about why the former yields (3 3 3 3)

Nevermind, got it, thanks

it worked for me

user> (map #(% 2 3) (list + / * -))
(5 2/3 6 -1)

@tsulej yes, it's the '(+ / * -) version that returns (3 3 3 3), seems + - / * are read as symbols and not as functions

Yeah if you do '() they're symbols not functions

ah, former, sorry

so ('+ 2 3) is trying to look up '+ in 2, failing, and returning default value 3

you can also use juxt for that

user> ((juxt + / * -) 2 3)
[5 2/3 6 -1]

oh neat, thanks

(map #((resolve %) 2 3) '(+ / * -))
=> (5 2/3 6 -1)

How would I generate a lazy seq of factorials?

e.g. 1 2 6 24...

Map factorial over range

=> (take 10 (map #(apply * % (range 1 %)) (iterate inc 1)))
(1 2 6 24 120 720 5040 40320 )

Is there a way to do it with corecursion? something like (this doesn't work) (def fact (lazy-cat [1] (map * fact (map inc fact))))

Yeah:

(def fac (lazy-cat [1] (map * fac (rest (range)))))

oo cool, thank you

🙂 @rauh’s solution is special to me because making that work was my first commit to the ClojureScript compiler. There is a cool Fibonacci sequence example like that in https://dev.clojure.org/jira/browse/CLJS-817

(def fib-seq (lazy-cat [0 1] (map + (rest fib-seq) fib-seq)))

Nice commit message 🙂

Hah! I was more diligent. 🙂

Is the exception shown by *e the complete stacktrace?

@devicesfor you can take the matter into your own hands and avoid whatever any REPL might be doing, by evaluating (.printStackTrace *e)

I was thinking about starting a “Elements of Clojure” book club. I posted some thoughts here: https://clojureverse.org/t/elements-of-clojure-book-club/1769 Feedback and possible participants welcome.

@devicesfor And of course some code may have caught the original exception and thrown their its own exception, which has the effect of obscuring the original stack trace. Not sure how common this still is in the Java world, but back when I was doing plain old Java it was an all to common thing to do in Java libraries.

I think I might be hitting that case 👍

I need some help interpreting part of the description of agent semantics on http://clojure.org - I'd welcome comments here. Here's the quote in question: > The actions of all Agents get interleaved amongst threads in a thread pool. At any point in time, at most one action for each Agent is being executed. Actions dispatched to an agent from another single agent or thread will occur in the order they were sent, potentially interleaved with actions dispatched to the same agent from other sources.

my question is about the last sentence and what it means for actions dispatched from 2 separate sources to be interleaved

I've been assuming that a single action runs until it is finished before yielding to another, regardless of the source

and I'd like it if that second sentence really means that given sources A and B, actions dispatched from both may be executed thus: A1 B1 A2 B2 A3 B3 etc

what I wouldn't like (which would cause me to rethink some things anyway) would be for actions A1 and B1 to be non-atomically interleaved

like A1.1 B1.1 A1.2 B1.2 etc

anyone got the truth to hand? If not, I'll write some kind of experiment later today to figure it out

actions from send or send-off are enqueued to be applied to an agent and can be interleaved. Each particular send or send-off function runs atomically. There will never be more than one thread applying an action on an agent at one time.

@alexmiller so does that mean that the A1 action (by my understanding, a function) may be partially executed, then paused, and B1 partially executed, paused, and then A1 completed?

no

A1 will complete, then B1

there is no “partial”

excellent, thank you for the clarification

is it true that defn- is considered not a good idea? wondering why if that's the case

@squarenegative This is an educational thread about private definitions https://groups.google.com/forum/#!topic/clojure/NolgUR4KLis

thanks

In particular, @alexmiller said "At one point all of the current metadata niceties didn't exist (used to be #^{:private true} some may recall) and defn- seemed worth doing I presume (pre-dates my involvementT). But then that was all simplified down to just ^:private and it's preferred to compose the pieces rather than copy N things."

what are people using as a library for very basic data visualization / charting?

was looking at Incanter, but it seems inactive

@krukow Incanter 1.9.2 was released last month. It is true that for a period it saw very little development, but it is usable.

There are a couple libraries that were recently mentioned in the #data-science channel.

thanks!

I’ll go with incanter

just a simple hobby project

I hit an interesting edge case with logging and macros, overcame it, and blogged about it: https://medium.com/@hlship/macros-meta-and-logging-575d5047924c

the 1.9 command line tools look interesting; we may be able to get rid of boot in some cases, except for the uberjar creation: can you make an uberjar with the clojure tool?

@clojurians873 there's this: https://github.com/healthfinch/depstar

thanks @sundarj, looks great

@sundarj i've also been pointed to http://github.com/juxt/pack.alpha which looks similar